This invention relates generally to a fusing apparatus employed in an electrostatographic printing machine, and more particularly concerns an apparatus for applying release material to a heated fuser member employed therein.
In the process of electrostatographic printing, a latent image is recorded on a surface and rendered visible with particles. These particles are transferred to a sheet of support material in image configuration. Thereafter, the particles are permanently affixed to the sheet of support material forming a copy of the original document thereon. Electrostatographic printing includes electrophotographic printing and electrographic printing. Electrophotographic printing employs a photoconductive member which is charged to substantially uniform level. A light image of an original document dissipates the charged photoconductive member recording a latent image of the original document thereon. Electrographic printing does not utilize a photoconductive member or a light image to create a latent image of the original document. However, in both of the foregoing processes, heat settable particles are generally employed to develop the latent image. After the particles are transferred to a sheet of support material, heat is applied thereto so as to permanently affix them to the sheet of support material.
Numerous techniques have been devised for applying heat to the particles transferred to the sheet of support material. One approach passes the sheet of support material, with the particles thereon, between a pair of opposed rollers. Frequently, the outer surface of the heated fuser roller is covered with polytetrafluoroethylene, commonly known as Teflon, to which a release agent such as silicone is applied. This Teflon layer may, preferably, have a thickness of several mils. The layer of oil applied thereto generally has a thickness of less than 1 micron. Silicone based oil possesses a relatively low surface energy and is particularly advantageous for use with Teflon. A thin layer of this oil is applied to the surface of the heated roller forming an interface between the roll surface and powder image on the sheet of support material. The low surface energy of this layer prevents the particles from transferring to the roller rather than remaining adhered to the sheet of support material. Thus, the particles are permanently affixed to the sheet of support material and do not smear or transfer to the roller.
Rather than employing a roller having a Teflon outer covering, a bare or heated metal roller may be utilized. When such a roller is employed, a low molecular weight polyethylene is applied thereto as a release agent. This release agent is generally a solid at room temperature. Prior techniques have maintained the release agent in its sump adjacent to the heated roller. As the fuser roller reaches the operating temperature, the release agent melts. However, it has been found that the life expectancy of polyethylene release material is greater in the solid state than in the liquid state. Thus, various techniques have been developed for articulating the release material as a solid bar so as to move it into and out of contact with the heated fuser roller. An example of such an approach is found in copending application Ser. No. 540,731 filed in 1975.
It is the primary object of the present invention to improve the apparatus employed to articulate a solid release material into and out of contact with a heated fuser member.